1990GT50

Well I really need to smog my truck and it's showing code 4 (check engine light).
WATER TEMPERATURE SENSOR SIGNAL--OPEN OR SHORT IN WATER TEMP. SENSOR SIGNAL
--WATER TEMPERATURE SENSOR CIRCUIT
--WATER TEMPERATURE SENSOR
--ECU

I replaced the temp sensor but that doesn't appear to be what the code calls for. Has anyone else had this code? How do i test the temp sensor? It it constant current or does it only recieve current when warm??? Help...

Thanks

Blue_petersen77

Maybe try tracing the wires to see if it's bare and touching metal anywhere.

1990GT50

It goes directly into the harness which seems untouched (huge bunch of tightly wrapped wires). I can't see any way it could be screwed up in the harness. I tried testing the plug which goes into the sensor today with the key in "on" position and neither side had power. Does it haveto be running or warmed up to test?

Blue_petersen77

I'd check fuses first. I doubt that has it's own fuse though. I'd try checking it again at running temp just outta curiosity. If still no response then it's probably in the harness somewhere.

4Crawler

iTrader: (3)

Factory Service Manual has testing procedures, typically a variable resistance related to coolant temperature. If the sender tests OK, repeat the resistance test from the appropriate pins of the ECU connector under the dash. Note that there are 2 or more temperature senders on the engine, which one did you replace (and what sort of engine is this referring to)?

1990GT50

Hey I really appreciate the help. Its on an 85 yota- 22RE. I replaced the coolant sensor for the ECU (in the front of the intake). My hanes has no testing procedures I could find. I should have bought the FSM........